1. Field of the Invention
The subject invention relates to the field of internet security and, more specifically, to validation of users accessing website.
2. Related Art
Providers of on-line information or services on the Internet often want or need to restrict access to the information or services offered on their websites. In many cases, simply allowing access to humans and not to a machine, e.g., a robot or crawler, provides some level of security against abuse for spam and other nefarious purposes. The method used today to ensure that the accessing party is human is called CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart) or Human Interactive Proofs. The idea behind CAPTCHAs is that there are tasks that humans are better at than computers. By providing a test easy for humans to solve but hard for computers, the service providers can increase the likelihood that their users are humans. The security bar is fairly low in that designers of CAPTCHAs only need to create CAPTCHAs that are sufficiently hard that it would be more economical to entice people to solve the CAPTCHAs than to create programs to solve them.
The commercially used CAPTCHAs often use a string of letters and digits randomly generated and morphed so they would be harder for optical character recognition (OCR) or other pattern recognition algorithms to recognize. However, there are also limitations to how much the letters can be distorted and yet be recognizable to humans. One often cited threshold is that humans' success rate should be 90%, while computers' should only be 0.01%. Even with a human success rate of 90%, the users will fail one out of ten trials which causes frustration towards the service provider. In addition, due to large individual variations in the human perceptual system, the distorted letters can be hard to read for many people and lead to exclusion of these users. For this reason it is highly desirably to create CAPTCHAs that are as easy as possible to solve by humans yet preserve or increase the difficulty for computers to solve them.
Some CAPTCHA designs, like logic puzzles or “which shape does not belong,” have the feel of intelligence tests. For many service providers it is not advisable to question their users' intelligence, especially when they want to have as many users as possible. Instead CAPTCHAs should be almost trivial for a person to solve.
All aspects of a service provider's webpages affect a user's impression of the company. CAPTCHAs are often prominent on corporate pages. For this reason, the aesthetics of the CAPTCHAs are important. Currently the aesthetical aspects of the CAPTCHAs are overlooked in comparison to the security aspects. In addition, previous research has shown that users' perception of beauty influences their perception of the ease of use. The majority of CAPTCHAs use degraded text, images, or audio, which not only make the CAPTCHAs less easy for humans, but also make them less attractive.
Therefore, there is a need in the art for improved CAPTCHAs that are easy for human, but very difficult for a machine to solve, yet appear aesthetically pleasing.